Comparative study of four glass ionomer luting cements during post pull-out tests

• Objectives. The aim of this study was to compare the maximum loads and modes of failure of four glass ionomer luting cements during post pull-out tests. • Methods. The cements studied included two based on conventional glass ionomer cement chemistry, i.e., a hand-mixed cement and an encapsulated cement, and two based on the newer light-cured chemistry, i.e., a restorative cement used at a low powder:liquid ratio and an experimental luting cement. One hundred and forty bovine incisors were cut 13 mm from the apex and prepared with post channels, 1.75 mm in diameter and 9 mm long. NiCrMb bonding alloy posts were cast and sandblasted prior to cementation into the roots with each of the cements. Twenty-four hours later, pull-out tests were carried out at a strain rate of 0.5 mm/min. The maximum loads and modes of failure were noted. The data obtained were analyzed using a Kruskal-Wallis test followed by comparison of groups using Mann-Whitney tests. • Results. Comparison of the maximum loads revealed a significant difference between the conventional encapsulated cement and all other cements. Weibull analysis of the results gave values for the Weibull moduli and probabilities of survival for a post under a given load for each cement and indicated that the newer cements performed better than the conventional cements. • Significance. Further research into the in vitro and in vivo behavior of the resin-modified glass ionomer cements in clinical situations where light-curing is not possible is justified.